ffixcth wrote:After reading the textbook and notes, i still don't understand what is "Negative Feedback" (something to do with Homeostasis) , can anyone explain what is Negative Feedback to me?

Here is a good article about hoomeostasis:
This article from Virology Journal (http://www.virologyj.com/home) might be of interest to the readership as it (among other things) describes a mechanism that enables protein information to modify RNA information, and is a mechanism of Larmarkian inheritance. The author makes it clear that it remains consistent with Darwinian selection. It also suggest potential weaknesses in viral replication that might be exploited.
Hepatitis C (HCV), hepatitis B (HBV), the human immunodeficiency viruses (HIV), and other viruses that replicate via RNA intermediaries, cause an enormous burden of disease and premature death worldwide. These viruses circulate within infected hosts as vast populations of closely related, but genetically diverse, molecules known as "quasispecies". The mechanism(s) by which this extreme genetic and antigenic diversity is stably maintained are unclear, but are fundamental to understanding viral persistence and pathobiology. The persistence of HCV, an RNA virus, is especially problematic and HCV stability, maintained despite rapid genomic mutation, is highly paradoxical. This paper presents the hypothesis, and evidence, that viruses capable of persistent infection autoregulate replication and the likely mechanism mediating autoregulation--Replicative Homeostasis--is described. Replicative homeostasis causes formation of stable, but highly reactive, equilibria that drive quasispecies expansion and generates escape mutation. Replicative homeostasis explains both viral kinetics and the enigma of RNA quasispecies stability and provides a rational, mechanistic basis for all observed viral behaviours and host responses. More importantly, this paradigm has specific therapeutic implication and defines, precisely, new approaches to antiviral therapy. Replicative homeostasis may also modulate cellular gene expression.

Firstly, Homeostasis refers to the existence of a stable internal environment in the organism, and this is usually done, by negative feedback.
Homeostatic regulations involve adjustments in physiological systems that are responsible for the preservation of homeostasis, and all body systems participate in homeostatic regulation. However, major roles are played by the nervous & endocrine systems.

3 characteristics of negative feedback:
1. Primary mechanism for homeostatic regulation.
2. Provides long term control over internal conditions and systems
3. Mechanism cause the variable to change
in a direction opposite to that of the initial change.

On the other hand, there's also positive feedback, which has the following 3 characteristics:
1. Mechanism enhances the original stimulus so that the activity is accelerated.
2. Important in control of physiological processes that once initiated must
be completed quickly.
3. Mechanism controls infrequent events that do not require continuous adjustments

ffixcth wrote:After reading the textbook and notes, i still don't understand what is "Negative Feedback" (something to do with Homeostasis) , can anyone explain what is Negative Feedback to me?

quote] THINK of it as someone pushing you, the first thing is push them back. same in the body: take a rise in temperature, the heat receptors in the skin sense it send a messange to the hypothalamus, which then responds by telling the body to sweat etc. this is negative feedback. Basically the system is trying to reach equilibrium by reversing a change made upon it. hope that helps!